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avatar_Audronic

Repairs to a CPC6128

Started by Audronic, 07:47, 03 November 15

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gerald

Quote from: Audronic on 22:34, 09 November 15
Thanks for the comment, I am unclear as to what you are saying could you expand the comment Please.
Q0 state is low most of the time in normal operation. So you cannot conclude that this pin is failing just by using the logic probe result.
Also, the keyboard errors you are seeing are related to Q9, not Q0.
- I would check that the keyboard connectors are OK (oxydation, solder)
- Check with a scope the shape of Q9 when you press a key and compare to an other working line. You will have to press a key that is controlled by that line to have valid result. Otherwise you will only see a open collector driver with no pull-up.

gerald

BTW, I am not saying the IC101 is fine, just that we cannot conclude from the logic probe results  ;) .

Audronic

@Gerald


Ok.  Thanks i will have a look with the CRO and do some comparisons.
Thanks for the update


Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Audronic

Damn  I have NO - 74LS145.
Even our local suppliers , Jaycar , Radio Parts have NIL stock
Oh well 3-4 weeks from China.
Unless any Australians know of a source ????


Thanks in anticipation    Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

pelrun


Audronic

@pelrun

Thanks for that.
I just ordered 3.

Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Audronic

The SAGA continues


The 74LS145 arrived NEXT day form R.S, this did not cure the Keyboard problem .
Also no sound out (Del Key).


Oh well onto the AY-3-8912 (28 PIN).
Unfortunately NONE available AT R.S, Radio Parts, Jaycar.
I have some coming on a SLOW boat from china.


It could be X-MASS before i get this up and running. :-X
a Nice beginners project. :doh:


Ray (Still smilling).

Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

AMSDOS

* Using the old Amstrad Languages :D   * with the Firmware :P
* I also like to problem solve code in BASIC :)   * And type-in Type-Ins! :D

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||C|-|E||

I wonder what happened to that CPC. So many faulty chips... maybe a strong discharge when it was working? the machine has the board almost unprotected  :-X

Audronic

@||C|-|E||


I purchased 2 CPC Machines KNOWING that they were faulty from a Gent in Tasmania (Just a little south from me).
I thought it might be a good Project to do some repairs on a new machine to me ( Previous TRS-80 Model 1/3/4/4p World ).
Its fine if the 6128 has a few problems I am learning heaps about them.
I am retired from paid work, this keeps the brain active.
I am having a guess that the machines have seen over voltage on the +5 volt line ??
The floppy drive is not working yet but it sort of performs, Motor runs, steps to try and find sectors,. reports errors to the screen so thats a start.
Anyway i will continue with the project.


Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

||C|-|E||

I know, I know  :) I have followed you progress and I think that is a very nice project. When I was saying that the machine has the board unprotected I meant that Amstrad produced them that way to save costs, so if the previous owner did something wrong probably half of the chips are fried  :) .

Bryce

I can send you an AY, but I doubt it's the AY that's bad, because the faulty keys are in the same column not row. I'd go back and check that the connection between the keyboard membrane and the LS145 are definitely good.

Bryce.

gerald

#37
Quote from: Audronic on 01:54, 11 November 15
The 74LS145 arrived NEXT day form R.S, this did not cure the Keyboard problem .
Also no sound out (Del Key).
I am with Bryce, the DEL key is also on line 9. Try the CLR key  ;)
Also beware that most chinese will sell you a AY-3-8912A which requires pull up to work on CPC.

Edit :  :doh:

Audronic

#38
The Keyboard Continuity Tests

I have just tested the continuity from the following
Keyboard connectors CP 002 (left- Under) and CP001 (Right- Over)

Pins on CP002    going to IC101 74ls145
(Left)
=======================================

Near AY Chip

Pin 11 (Common Line)
Pin 12                    Pin 10
Pin 13                    Pin  9
Pin 14                    Pin  7
Pin 15                    Pin  6
Pin 16                    Pin  5
Pin 17                    Pin  4
Pin 18                    Pin  3
Pin 19                    Pin  2
Pin 20                    Pin  1

=======================================
Pins on CP001    going to IC102 AY-3-8912
(Right)
=======================================

Near AY Chip

Pin 1 (N/C)              =====
Pin 2                    Pin 14
Pin 3                    Pin 13
Pin 4                    Pin 12
Pin 5                    Pin 11
Pin 6                    Pin 10
Pin 7                    Pin  9
Pin 8                    Pin  8
Pin 9                    Pin  7
Pin 10 (N/C)             =====

=======================================
The Keyboard Matrix drawing that i am using is from the
""service.manual.464plus.6128plus "" Page 11 Key Matrix (Applies to 464 & 6128)
Is This what you requested, I have tried 2 Working keyboards -- all the same problem.

Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

gerald

I don't know what my brain did these days  :picard:

All your failing keys are all on ROW 7 -> Which point to an AY problem !

Bryce

Is the plus and classic matrix the same? It's a Classic 6128 that he's fixing.

Bryce.

gerald

Quote from: Bryce on 12:48, 11 November 15
Is the plus and classic matrix the same? It's a Classic 6128 that he's fixing.

Bryce.
All matrix are the same.
But just look at the matrix table and you will  :doh: as well  ;)

hint : del z x v space , . ctrl ...

Bryce

Quote from: gerald on 14:03, 11 November 15
All matrix are the same.
But just look at the matrix table and you will  :doh: as well  ;)

hint : del z x v space , . ctrl ...

I saw that the other night, but that was after about 15 beers, so I still thought it pointed at the 145 for some reason.  ::)

Bryce.

Audronic

#43


As there has been some comments about 2 versions of the AY-3-8912  " AY-3-8912 and AY-3-8912A "
I was just Looking at the AY Chip and took this Photo.
I was wondering if these holes could be used for the Pullup Resistors (Pack)
If so what Value Please.
Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

gerald

Quote from: Audronic on 23:31, 11 November 15
I was wondering if these holes could be used for the Pullup Resistors (Pack)
Yes, these are indded for a resistor network.
Quote from: Audronic on 23:31, 11 November 15
If so what Value Please.
I would say 2.2K.
This is what is used on the Plus schematics. On CPC, this networks is not on the schematics and does not have a reference.

Audronic

@gerald


Ok, I had a look at the CPC464+ Service Manual and the Resistor Networks (2.2k) were added.
Would that have been for greater signal stability ?.
Do we need them for the 464/6128.


Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Bryce

No it's because the non-version already has these pull-ups inside the chip. The holes are just a fallback in case they couldn't source the right version at the right price.

Bryce.

1024MAK

What results do you get when measuring pin 7 of the AY sound chip?


If you simulate a key by using a suitable wire to pretend to be a key, connected directly between an appropriate output pin of the 74LS145 and pin 7 of the AY sound chip, does this produce the correct response?


Mark
Looking forward to summer in Somerset :-)

Audronic

#48
Hi Mark


What results do you get when measuring pin 7 of the AY sound chip?

Normally sitting HI without the Keyboard connected

If you simulate a key by using a suitable wire to pretend to be a key, connected directly between an appropriate output pin of the 74LS145 and pin 7 of the AY sound chip, does this produce the correct response?

If I simulate the letter  "a" (Pins 7 and 12)I get NO pulse on the probe  and the letter " a " On the screen

If I simulate the letter  "z" (Pins 9 and 12)I get a pulse on the probe (HI & Pulse) and NOTHING On the screen

Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Audronic

Added extra information to the Keyboard Table.


I have just tested the continuity from the following
Keyboard connectors CP 002 (left- Under) and CP001 (Right- Over)

Pins on CP002    going to IC101 74ls145    Called   Activity
(Left)                                    X? or Y?
==========================================================

Near AY Chip

Pin 11 (Common Line)                         Y10     Pulse
Pin 12                    Pin 10             Y9      Pulse
Pin 13                    Pin  9             Y8      Pulse
Pin 14                    Pin  7             Y7      Pulse
Pin 15                    Pin  6             Y6      Pulse
Pin 16                    Pin  5             Y5      Pulse
Pin 17                    Pin  4             Y4      Pulse
Pin 18                    Pin  3             Y3      Pulse
Pin 19                    Pin  2             Y2      Pulse
Pin 20                    Pin  1             Y1      LO  Pulse on the probe BUT looks just above ground on CRO.

Front of Computer
==========================================================
Pins on CP001    going to IC102 AY-3-8912
(Right)
==========================================================

Near AY Chip

Pin 1 (N/C)              =====                      O/C
Pin 2                    Pin 14             X1      HI
Pin 3                    Pin 13             X2      HI
Pin 4                    Pin 12             X3      HI
Pin 5                    Pin 11             X4      HI
Pin 6                    Pin 10             X5      HI
Pin 7                    Pin  9             X6      HI
Pin 8                    Pin  8             X7      HI
Pin 9                    Pin  7             X8      HI
Pin 10 (N/C)             =====                     O/C

Front of Computer
==========================================================
Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

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